Process for the after-treatment of phosphatized metal articles

ABSTRACT

A PROCESS FOR THE AFTER-TREATMENT OF PHOSPHATIZED METAL ARTICLES, WHICH PROCESS COMPRISES TREATIN THE PHOSPHATIZED SURFACE OF THE METAL ARTICLES WITH A NON-AQUEOUS SOLUTION CONTAINING A NOVOLAC PHENOL-FORMALDENYDE RESIN HAVING A MOLECULAR WEIGHT OF FROM ABOUT 300 TO ABOUT 5,000, AND THEREAFTER BAKING THE TREATED ARTICLE AT A TEMPERATURE OF AT LEAST 190*C. IN THE PRESENCE OF AN OXYGENCONTAINING ATMOSPHERE. THE ARTICLES SO TREATED ARE RENDERED EXCEPTIONALLY RESISTANT TO CORROSION AND TO UNDERCUTTING WHEN COATED WITH FINAL FINISH COATINGS.

United States Patent 3,749,611 PRQCESS FOR THE AFTER-TREATMENT F PHOSPHATIZED METAL ARTICLES Edward Leon, Parkersburg, W. Va., and Malcolm H.

Shatz, Williamsviile, N.Y., assignors to Hooker Chemical Corporation, Niagara Falls, N.Y. No Drawing. Filed Dec. 28, 1970, Ser. No. 102,257 Int. Cl. (323i 7/08 US. Cl. 1486.15 R 24 Claims AESTRACT OF THE DISCLOSURE A process for the after-treatment of phosphatized metal articles, which process comprises treating the phosphatized surface of the metal articles with a non-aqueous solution containing a novolac phenol-formaldehyde resin having a molecular weight of from about 300 to about 5,000, and thereafter baking the treated article at a temperature of at least about 190 C. in the presence of an oxygencontaining atmosphere.

The articles so treated are rendered exceptionally resistant to corrosion and to undercutting when coated with final finish coatings.

This invention relates to the chemical treatment of metal articles. More particularly, this invention relates to the chemical treatment of metal articles to render the metal articles exceptionally corrosion-resistant, better suited to retain final finish coatings, and resistant to undercutting when final finish coatings are so applied.

It is well known that bonding coatings are desirable on metal articles to protect such articles from corrosion and to form a base to promote adherance to such surfaces of organic finishes such as paints, enamels, lacquers, siccative coatings and the like. A variety of processes have been developed for this purpose and many specifically different compositions have been proposed as satisfactory for use in such processes.

Presently, the majority of bonding coating techniques entail the use of phosphate solutions, or phosphatizing solutions. Such phosphatizing solutions as have been used for the purpose of inhibiting the corrosion of such as iron and steel surfaces result in phosphate coatings which, however, do not provide sufiicient protection against corrosition of the metal in many cases. In order to obtain effective protection against corrosion, the phosphatizing process has been followed in the past, in most instances, by rinsing with dilute chromate solutions.

However, this chromate after-rinsing or after-treatment of the phosphate coating has given rise to, among other things, serious disposal problems relative to the resulting waste water. Because of the toxicity of the hexavalent and trivalent chromium, these materials must be removed almost quantitatively from the waste water prior to disposal. Such recovery processes as must be practiced render the chromate rinse economically less desirable. Further, the chromic acid concentrates used for preparing and replenishing the rinsing bath present additional difficulties in handling clue to their strongly corrosive properties. The use of chromate resins in some instances also gives rise to other practical difiiculties. During some applications, excessive amounts may tend to either discolor to bleed through subsequently applied topcoats. In other applications, the solutions may also tend to run or to pool in confined areas of the metal article workpiece, which may cause subsequent loss of topcoat adhesion when the completed article is subjected to high humidity conditions. Because of the running and pooling of the chromate rinsing solution, certain areas of the metal articles are inherently left deficient in rinse treatment. Such areas exhibit as a result poor corrosion-resistance and poor resistance to undercutting when exposed to corrosive atmospheres.

Attempts to eliminate or to modify the sealing chromium rinse by post-treating the phosphatized metal articles with solutions of such coating materials as alkene phosphinic acids, acrylics, epoxies and the like have not resulted in the production of entirely satisfactory corrosion-resistant metal articles, generally, having the anti-corrosive and paint adhesion properties attributed to chromimurn-phosphatized metal substrates.

It is an object of the present invention to provide for protective coatings for corrodible metal articles.

It is is a further object of the present invention to provide protective coatings for corrodible metal articles which are receptive to retaining final finish coatings.

It is yet another object of the present invention to provide a chemically reactive metal-treating composition which will, when applied to phosphatized metal articles, render such metal articles exceptionally corrosion-resistant.

These and other objects will become readily apparent in view of the following description of the present invention.

According to the present invention, an anti-corrosive and paint-receptive and retentive film is formed on a metal article by the process comprising:

(a) coating the metal article with a conventional phosphatizing solution;

(b) treating the phosphatized surface thereof with a nonaqueous solution of a novolac phenol-formaldehyde resin having a molecular weight of from about 300 to about 5,000; and

(c) thereafter baking the treated metal article at a temperature of at least about C. in the presence of an oxygen-containing atmosphere.

The use of phenolic resins to prevent corrosion and to provide a measure of protection to metal articles is well known and established in the art. However, such value has been achieved by the use of very high molecular weight phenolic resins forming relatively thick, contiguous films, the molecular weight of such phenolic resins varying from about 20,000 to greater than 100,000.

It has now been found that very low molecular weight novolac phenol-formaldehyde resins applied to phosphatized metal articles to deposit amounts as small as 4.0 milligrams to resin per square foot, and generally from about 50 to about 400 milligrams of resin per square foot, and subsequently heated to temperatures in excess of about 190 C. in the presence of an oxygen-containing atmosphere provide for remarkably superior corrosion protection and other performance properties, and do not behave as barrier layers, as do the high molecular weight phenolic resins currently used in the art. Apparently, when the phosphate and low molecular weight novolac containing compositions are heated to temperatures in excess of about 190 C. in the presence of an oxygen-containing atmosphere, the resins tend to exhibit chemical, rather than contigous, behavior. It is believed (I) on I OH I OH on,- ornand OH OH OH:-

wherein a is an integer having a value on the order from 1 to about 26 and b is an integer having a value on the order of from about 1 to about 13. Such novolac phenolformaldehyde resins as are represented by Formula I, designated as ortho-novolacs, are substantially phenolterminated chain polymers in which the phenolic nuclei are united by methylene bridges, for the most part located ortho to the phenolic hydroxyl groups. Those novolac phenol-formaldehyde resins as are represented by Formula II, designated as random novolacs, are substantially phenol-terminated chain polymers in which the phenolic nuclei are united by methylene bridges, for the most part located ortho and para relative to the phenolic hydroxyl groups.

Such resins are further characterized as permanently soluble and thermoplastic, and curable to insoluble, infusible products upon the application of heat, or upon the addition thereto of a source of formaldehyde.

The resins are of adequate hardness, with a softening temperature of from about 50 to about 110 C., to permit grinding thereof, exhibit good curing properties including a fast rate of cure, and attain a high degree of strength upon being cured.

Such novolac resins finding utility in the present process can be prepared by any one of a number of suitable methods known in the art, such as those disclosed in US. Pat. 2,475,587 ,and 3,108,978, in Modern Plastics, No. 6, 136, 220 (1953), and Journal of Polymer Science 22, 477 (1956), the teachings of which are herein incorporated by reference. The preparation of a typical acidcatalyzed novolac is as follows.

A reaction vessel is charged with 1 mole of phenol per 0.8 mole of Formalin. Approximately 0.2 to 0.3 percent sulfuric acid, based on the phenol, is added following dilution of about 1 N with water. Following the exothermic reaction on the addition of the catalyst, the reaction mixture is heated to reflux for approximately two hours. The resin is then neutralized with lime in a water slurry, dehydrated under reduced pressure, and discharged from the reaction vessel at elevated temperatures. Following a cooling period, the resin is then ground to the desired particle slze.

Application of the novolac phenolic resins to the phosphatized metal articles to be treated is preferably accomplished by solution application. Suitable solvents include such organic materials as ketones, lower alcohols, halogenated hydrocarbons, aromatic hydrocarbons and the like. Exemplary of suitable ketones are acetone, methyl ethyl ketone and the like. Exemplarly of suitable lower alcohols are methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, tertiary butyl alcohol and the like. Exemplary of suitable aromatic hydrocarbons are benzene, toluene, xylene and the like. Exemplary of suitable halogenated hydrocarbons are carbon tetrachloride, trichloroethylene, trichloroethane, tetrachloroethane, perchloroethylene and the like. Compatible mixtures of suitable solvents may also be used, if desired. Preferably, however, the solvent used is either acetone or trichloroethylene.

The non-aqueous resin treating solution is generally formulated in such a manner as to provide a solution containing from about 3 to about 10 percent by weight of the novolac resin. Preferably, those solutions containing from about 3 to about 7 percent by weight of novolac resin are employed. However, the use of more or less concentrated solutions is not hereby precluded.

The non-aqueous resin treating solution may also contain such additional materials as coloring agents, antismudging agents, stabilizers and the like, generally in amounts not exceeding about 5 percent by weight. Calcium hydroxide may be added to assist in stabilizing the resin treating solution, generally in an amount of from about 0.2 percent by weight to about the maximum solubility of the hydroxide in the resin solution.

The novolac resin treating solution may be applied to the phosphatized metal article either by spraying or by immersing the article in the solution, or by any other suitable means, to deposit resin in an amount of less than about 400 milligrams per square foot on the phosphatized metal article, generally in amounts less than about milligrams per square foot. After the article has been treated, the solvent is removed by any suitable means, such as by flashing, and the article is then heated at temperatures of at least about 190 C., generally from about 190 to about 270 C., and preferably at about 205 C., in the presence of an oxygen-containing atmosphere for a period of from about 15 seconds to about 5 minutes.

The time required to effect the heating step is, of course, dependent upon the makeup of the resin treating composition, the temperature employed and the nature of the article being treated. Generally, at a temperature of about 205 C., a finished treatment is effected in less seconds.

The surface of the metal article, following the heat treatment, is highly adherent and receptive to and retentive to the application of paints, varnishes and lacquers. Thus, metal articles, treated according to the process of the present invention, may receive organic finishes having an end use as automobile finishes, exterior trim coatings on metal building panels, appliance coatings, metal furniture coatings and the like.

Metal surfaces which may be treated according to the process or the present invention include the ferrous metals, aluminum, galvanized metals, alloys and the like.

The deposition of the phosphate coating may be eifected by any of the conventional phosphatizing procedures. Aqueous phosphatizing solutions are generally prepared by dissolving in Water small amounts of phosphoric acid and a metal salt such as a nitrate, phosphate, nitrite, sulfate, chloride or bromide of sodium, manganese, zinc cadmium, iron, lead, nickel, copper or aluminum. Preferably the metal salt used is one which, in aqueous solution, will yield zinc or alkali metal ions.

An oxidizing agent such as sodium chlorate, sodium perbora-te, sodium nitrite, potassium permanganate, or hydrogen peroxide can be included in the phosphatizing solution to depolarize the metal surface being treated and thereby increase the rate at which the phosphate coating is formed on the metal article. Other auxiliary agents such as anti-smudging agents, coloring agents, metal cleansing agents and the like may also be incorporated in the phosphatizing solution. A common type of commercial phosphatizing bath which contains zinc ions, phosphate ions and a depolarizer is made by dissolving small amounts of zinc phosphate, sodium nitrate and phosphoric acid in water.

The phosphatizing solutions suitable for use in the process of the present invention can also be formulated conveniently by first dissolving zinc nitrate, calcium nitrate and the like in sufiicient water to yield the desired concentration of ions and afterward adjusting the acidity with phosphoric acid. Another type of commercial phosphatizing bath is one containing zinc ions, nitrate ions, phosphate ions and either nitrite or chlorate ions as a depolarizer.

However, the present process is not dependent upon the use of a particular phosphatizing solution, and any of the several commercial aqueous phosphatizing solutions commonly used in the art may be employed to phosphatize the surface of metal articles to be treated according to the present process. As previously stated, the preferred commercial phosphatizing solutions are those which, on being deposited on metal substrates, will yield zinc or alkali metal phosphates.

In the accepted practice of phosphatizing a metal article, the surface thereof is usually cleansed by physical and/ or chemical means such as immersion in or spraying with an aqueous caustic cleanser, mechanical abrading or polishing, vapor degreasing and the like. For the purpose of the present process, it is preferred to cleanse the metal article to be phosphatized and subsequently treated with the novolac treating solutions by immersing the article for a period of about 60 seconds in a commercial aqueous caustic metal cleanser at a temperature of about 60 C. Following the cleansing of the metal article, the article is generally rinsed with hot water to prevent contamination of the phosphatizing solution.

The application of the phosphatizing solution to the metal article prior to the application of the novolac resin treating solution may be accomplished by any suitable means known in the art. Because the phosphatizing solutions are generally applied to temperatures on the order of from about 50 to about 85 C., spray-phosphatizing techniques generally are used. Immersion techniques are also well adapted to providing phosphate coatings on metal articles to be subsequently resin treated. The manner of application, however, is not important in that quiescent baths can be used, or continuous baths can be advantageously employed.

The aqueous phosphatizing solution is generally maintained at temperatures on the order of from about 50 to about 85 C. Preferably, temperatures on the order of from about 60 to about 70 C. are employed.

Satisfactory phosphate coatings, when applied in accordance with the procedures previously detailed, result in about 60 seconds. Longer or shorter times may be realized by varying the concentration of the phosphatizing solution and the temperature employed.

Upon completion of the phosphatizing step, the phosphate coated metal articles are rinsed with cold Water.

It has been found that the wet phosphate coated articles, following the rinsing step, may be immediately treated with the non-aqueous novolac resin treating solution, and that it is not necessary to remove the water present, whether present as a result of the application of the aqueous phosphatizing solution or as a result of the postphosphatizing cold water rinse. While the phosphatized metal articles may be subjected to a drying step prior to the application thereto of the novolac resin treating solution, no adverse effect on the finished coating, or to subsequently applied topcoat results when the procedure of the present process is followed, and the post-rinse drying is omitted. For example, the wet phosphatized article is immersed in a trichloroethylene-novolac resin treating composition at about C. When the article is removed, the trichloroethylene flashes off. The mixture of trichloroethylene and water condensate may then be collected by any suitable means, separated and the trichlorethylene recycled to the treating step. The treated article is then subjected to the heating step.

Generally, however, it is preferred to subject the phosphatized metal articles to a drying step of from about to about 160 C. for a period of from about 30 to about seconds following the rinse and prior to the application of the novolac resin treating composition thereto.

The temperature of the novolac resin treating com.- position is preferably maintained at a temperature of from about 80 to about 90 C. during application to the phosphatized metal articles and the treated metal articles are subsequently baked at a temperature of from about 190 to about 275 C., preferably at a temperature of from about 205 to about 270 C., for a period of from about 15 to about seconds.

The following examples serve to illustrate the present invention but are not to be construed as limiting it thereto.

Following the resin treatment of the metal articles in the following examples, each was painted with enamel and then subjected to 5 percent salt spray and physical tests. The salt spray test is the American Society for Testing and Materials (ASTM) test B117-61 with painted panels scribed as given in .ASTM test D-l6546l. This employs a 5 percent sodium chloride fog. The ratings given depend on the creepage from the scratch, given in of an inch. Ratings given as spot (S) indicate no creepage except in a small area. In the salt spray test, unless otherwise indicated, the exposure time was 120 hours. In the physical test, arhesion was determined by knife blade and the results are reported on the scale of 0 to 10, where 10 is excellent, 8 is good, 6 is fair, 4 is poor, 2 is very poor, 0 is complete loss of adhesion.

EXAMPLE 1 A polished steel panel is cleaned for 60 seconds in a commercial hot caustic cleanser, rinsed with hot water and dipped for 150 seconds in an aqueous commercial zinc phosphate phosphatizing solution maintained at a temperature of about 75 C. The phosphatized panel is then rinsed with cold Water, air-dried and immersed for 90 seconds in a solution of trichloroethylene containing 5 percent by weight of ortho-novolac resin (MW 820) and 0.2 percent by weight calcium hydroxide, based on the weight of resin. During the treatment, the temperature of the treating solution is maintained at about 86 C. Following removal of the panel from the resin treating solution, the solvent is removed and the treated panel heated at a temperature of about 205 C. for a period of 150 seconds in an air-circulating oven. The treated panel has less than 400 milligrams/ft. of resin deposit and when topcoated with commercial melamine alkyd enamel, exhibits a knife blade adhesion rating of 10, an undercutting of less than A of an inch when exposed to extended salt fog, a 98 percent paint retention and no blisters when subjected to 100 percent huimidity for 1000 hours.

EXAMPLE 2 EXAMPLE 3 The procedure of Example 1 is observed with the exception that the treated panel is topcoated with commercial acrylic topcoating. Similar excellent results are obtained as in Example 1.

EXAMPLE 4 A polished steel panel is cleansed for 60 seconds in a commercial hot caustic cleanser, rinsed with hot water and dipped for 180 seconds in an aqueous commercial zinc phosphate phosphatizing solution maintained at a temperature of about 75 C. The phosphatized panel is then rinsed with cold water, air-dried and immersed for 90 seconds in a solution of trichloroethylene containing 8.2 percent by weight of ortho-novolac resin (MW 306) and 0.2 percent by weight calcium hydroxide, based on the weight of resin. During the treatment, the temperature of the resin treating solution is maintained at about 86 C. Following removal of the panel from the resin treating solution, the solvent is removed and the treated panel heated at a temperature of about 205 C. for a period of 150 seconds in an air-circulating oven. The treated panel has less than 100 milligrams/ft. of resin deposit and when top-coated with commercial alkyd enamel exhibits a knife blade adhesion rating of 10, an undercutting of A th of an inch when exposed to extended salt fog and a 96 percent paint retention.

EXAMPLE 5 The procedure of Example 4 is observed with the exception that, following the heating step, the treated panel is washed with fresh trichloroethylene vapor and flashed dry. Similar excellent results obtain as in Example 4.

EXAMPLE 6 The procedure of Example 4 is observed with the exception that the panel is washed with trichloroethylene vapor, flashed and then subjected to the heating treatment. Similar excellent results obtain as in Example 4.

EXAMPLE 7 A polished steel panel is cleansed in trichloroethylene and wiped dry. Following immersion treatment in commercial zinc phosphatizing solution, the panel is cold water rinsed and blotted dry with an adsorbent towel. The damp panel is immersed in a 5 percent by weight orthonovolac (MW 1000) in boiling trichloroethylene saturated with calcium hydroxide. Following removal of the panel from the bath, the panel is heated at 270 C. for a period of 60 seconds in an air-circulating oven. The panel has a knife blade adhesion rating of 9, a paint retention of 99 percent, an undercutting of less than of an inch, and a resin deposit of less than 400 mg./ft.

EXAMPLE 8 The procedure of Example 7 is observed with the exception that the panel is heated for a period of 90 seconds. The panel, when topcoated, exhibits a knife blade adhesion of greater than 9, a paint retention of 99 plus percent and an undercutting of less than 5 of an inch when exposed to long term salt fog.

EXAMPLE 9 The procedure of Example 7 is observed with the exception that the panel is heated for 60 seconds at 205 C. Similar results obtain as in Example 7.

EXAMPLE 1 The procedure of Example 9 is observed with the exception that the panel is heated for 90 seconds. Similar results obtain as in Example 8.

EXAMPLE 1 1 The procedure of Example 9 is observed with the exception that the panel is heated for 120 seconds. Similar excellent results obtain as in Example 8.

EXAMPLE 12 A polished steel panel is cleansed with commercial hot caustic, hot water rinsed and given a conventional iron phosphate treatment for 150 seconds. The phosphatized panel is then cold water rinsed, drained and immersed in a solution of trichloroethylene, percent by weight orthonovolac (MW 1000) and calcium hydroxide to the point of saturation. Following the immersion in the resin treating solution, the panel is flashed dry and heated at 190 C. for a period of 30 seconds. The panel, when topcoated with commercial melamine alkyd enamel, has a knife blade rating of greater than 9, an undercutting of V of an inch, and a paint retention of 96 percent.

EXAMPLE 13 The procedure of Example 12 is observed with the exception that the heating step is conducted for a period of 60 seconds. Similar excellent results are obtained as in Example 12.

EXAMPLE 14 The procedure of Example 12 is observed with the exception that the heating is conducted at 190 C. for a period of seconds. Similar excellent results obtain as in Example 12.

EXAMPLE 15 The procedure of Example 12 is observed with the exception that the heating is conducted at 190 C. for a period of seconds. Similar excellent results obtain as in Example 12.

EXAMPLE 16 The procedure of Example 12 is observed with the exception that the panel is heated at 205 C. for a period of 30 seconds. Similar excellent results obtain as in Example l2.

EXAMPLE 17 The procedure of Example 16 is observed with the exception that the panel is heated for 60 seconds. Similar excellent results obtain as in Example 12.

EXAMPLE 18 The procedure of Example 16 is observed with the exception that the panel is heated for a period of 90 seconds. The panel, when topcoated, has a knife blade adhesion rating of 9, a paint adhesion of 97 percent and an undercutting of less than of an inch when subjected to extended salt fog.

EXAMPLE 19 The procedure of Example 16 is observed with the exception that the treated panel is heated for a period of 120 seconds. Similar excellent results obtain as in Example 18.

EXAMPLE 20 The procedure of Example 12 is observed with the exception that the resin-treated panel is heated at 270 C. for a period of 60 seconds. The panel, when topcoated, has a knife blade adhesion rating of greater than 9, a paint retention of 97 percent and an undercutting of less than of an inch when subjected to extended salt fog.

EXAMPLE 21 The procedure of Example 20 is observed with the exception that the panel is heated for a period of 90 seconds. Similar excellent results obtain as in Example 20.

EXAMPLE 22 A polished steel panel is cleansed for 60 seconds in a commercial hot caustic cleaner, rinsed with hot water and dipped for seconds in an aqueous commercial zinc phosphate phosphatizing solution maintained at a temperature of 75 C. The phosphatized panel is then rinsed with cold water and oven flashed for 60 seconds at a temperature of C. The dried panel is immersed for 30 seconds in a solution of trichloroethylene containing 7 percent by weight ortho-novolac resin (MW 1000) and 0.2 percent by weight calcium hydroxide, the solution maintained at a temperature of 70 C. to deposit less than about 400 milligrams of resin per square foot. Following removal of the panel from the resin treating solution, the treated panel is heated at a temperature of about 270 C. for a period of 90 seconds in an air circulating oven.

After 6 hours of exposure to percent salt spray, the treated panel is markedly less corroded than a panel treated by phosphatizing alone. A similarly treated panel is topcoated with a commercial melamine alkyd enamel. After 120 hours exposure to 5 percent salt spra the panel exhibits a knife blade adhesion of 9, an undercutting of A of an inch and topcoat retention of 95 percent.

EXAMPLE 23 The procedure of Example 22 is observed With the exception that the panel treated With the novolac resin treating solution is heated at 270 C. for a period of 90 seconds in an air circulating oven after immersion in the resin treating solution for 60 seconds. The panel exhibits a knife blade adhesion of 9, a creepage of less than 1 and a topcoat retention of 93 percent.

EXAMPLE 24 The procedure of Example 23 is observed with the exception that the panel is heated for 120 seconds. The treated panel exhibits excellent anti-corrosive and paint adhesion properties.

EXAMPLE 25 The procedure of Example 22 is observed with the exception that the panel is immersed in the resin treating solution for a period of 90 seconds. Similar excellent results obtain as in Example 22.

EXAMPLE 26 The procedure of Example 25 is observed with the exception that the treated panel is heated for a period of 120 seconds. Similar excellent results obtain as in Example 22.

EXAMPLE 27 The procedure of Example 22 is observed with the exception that the panel is immersed in the resin treating solution for 120 seconds, and the panel is heated at 270 C. for 30 seconds. Similar excellent results obtain as in Example 22.

EXAMPLE 28 The procedure of Example 27 is observed with the exception that the treated panel is heated for 90 seconds. Similar excellent results obtain as in Example 22.

EXAMPLE 29 A polished steel panel is immersed for 60 seconds in a commercial hot caustic cleanser, hot water rinsed and given a conventional iron phosphate treatment. Following oven flashing, the panel is immersed for 60 seconds in a 5 percent by weight solution of orthonovolac (MW 1000) in trichloroethylene, removed and heated at 270 C. for a period of 60 seconds in an air-circulating oven. The treated panel has a knife blade adhesion rating of 9, an undercuting of less than of an inch and a paint retention of greater than 98 percent.

EXAMPLE 30 The procedure of Example 29 is observed with the exception that the panel is heated for 90 seconds. Similar excellent results obtain as in Example 29.

EXAMPLE 31 The procedure of Example 29 is observed, with the exception that the treated panel is heated at 270 C. for 120 seconds. Similar excellent results obtain as in Example 29.

EXAMPLES 32-35 Four panels are treated in accordance with the procedure of Example 29, with the exception that the novolac resin treating composition contained no calcium hydroxide, the orthonovolac resin content is 3 percent by Weight, the immersion time in the resin treating composition is 10 60 seconds and the treated panels are heated at 270 C. for periods of 30, 60, 90 and 120 seconds. Similar excellent results obtain as in Example 29.

EXAMPLES 3 6-3 9 Four panels are treated in accordance with the procedure of Examples 32-35 with the exception that the resin content is 7 percent by weight. Similar excellent results obtain as in Example 29.

EXAMPLES 40-43 Four panels are treated in accordance with the procedure of Examples 32-35 with the exception that the resin content is 1 percent by weight. Similar excellent results obtain as in Example 29.

EXAMPLE 44 A polished steel panel is cleansed for 60 seconds in a commercial hot caustic cleanser, rinsed with hot water and then immersed for 180 seconds in a commercial zinc phosphatizing solution maintained at a temperature of C. The phosphatized steel panel is then rinsed with cold Water and the easily removable excess water removed with laboratory compressed air. The damp phosphatized steel panel is then immersed for 120 seconds in 70 C. trichloroethylene containing 5 percent by weight orthonovolac resin having a molecular weight of about 1000 and suflicient calcium hydroxide to saturate the solution, to deposit less than about 400 milligrams of resin per square foot on the treated panel. The treated panel is then heated at 205 C. in an air circulating oven for a period of seconds, and topcoated with commerical melamine alkyd enamel. No damage is evidenced when the panel was subjected to a percent humidity test for 1020 hours, and similar excellent results obtained when the panel was subjected to a. 5 percent standard salt fog test.

EXAMPLES 45-46 The procedure of Example 44 is observed with the exception that the treated panels are heated at 205 C. for periods of and seconds. Similar excellent results obtain as in Example 44.

EXAMPLES 47-49 The procedure of Example 44 is observed with the exception that the treated panels are heated at 190 C. for periods of 90, 120 and seconds. Similar excellent results obtained as in Example 44.

EXAMPLES 50-5 2 The procedure of Example 44 is observed with the exception that the cleansed panels are subjected to a spray of commercial phosphatizing solution for a period of 90 seconds, and the treated metal panels are heated at 205 C. for periods of 90, 120 and 150 seconds. Similar excellent results obtain as in Example 44.

EXAMPLES 53-55 The procedure of Examples 50-52 is observed with the exception that the treated panels are heated at C. for periods of from 90, 120 and 180 seconds. Similar excellent results obtain as in Example 44.

EXAMPLE 56 A polished steel panel is cleansed in a commercial hot caustic cleanser, rinsed with hot water, and treated with commercial zinc phosphate phosphatizing solution at 60 C. for 180 seconds. The phosphate-coated panel is then rinsed with cold Water, dried at 160 C. for 90 seconds and rinsed in trichloroethylene vapors. The rinsed panel is immersed in a solution of 5 percent by weight orthonovolac resin in trichloroethylene saturated with calcium hydroxide for 60 seconds. Following the immersion the panel is rinsed in trichloroethylene vapors and heated at 205 C. for 150 seconds. The treated panel has less than 30 milligrams/ft. deposited thereon, exhibits an undercutting of less than of an inch when exposed to extended salt fog, and has a paint retention of 99 percent.

EXAMPLE 57 The procedure of Example 56 is observed with Lhe exception that the panel is heated at 205 C., rinsed with trichloroethylene vapor and subjected to a final heating at 205 C. for 150 seconds. Similar excellent results obtain as in Example 56.

EXAMPLE 58 The procedure of Example 56 is observed with the exception that the panel is subjected to heating with no trichloroethylene rinse. Similar excellent results obtain as in Example 56.

EXAMPLE 59 The procedure of Example 56 is observed with the exception that the panel is rinsed in trichloroethylene vapor following the heating step. Similar excellent results obtain as in Example 56.

EXAMPLE 60 A polished steel panel is cleansed for 60 seconds in a commercial hot caustic cleanser, rinsed with hot water and subjected to a spray of a commercial zinc phosphate solution at 60 C. for 60 seconds. The phosphatized panel is then rinsed with cold water and the rinse water removed by heating the panel in a circulating air oven for 90 seconds at 160 C. The panel is dipped into a solution of commercial oxalic acid-catalyzed random novolac (MW=350) dissolved in acetone at a concentration of percent by weight, for a period of 60 seconds.

Following removal from the resin treating composition, the treated panel is heated at a temperature of 205 C. for a period of 150 seconds. The treated panel is topcoated with commercial melamine alkyd enamel. The adherence of the enamel was excellent as was the corrosion resistance of the panel as determined by the standard testing.

EXAMPLE 61 The procedure of Example 60 is observed with the exception that the random novolac resin is a sulfuric acid catalyzed random novolac (MW 540). Similar excellent results obtain as in Example 60.

EXAMPLE 62 The procedure of Example 60 is observed with the exception that the random novolac resin is a sulfuric acidcatalyzed random novolac (MW 876). Similar excellent results obtain as in Example 60.

What is claimed is:

1. A process for the after-treatment of a phosphatized metal substrate which comprises contacting said metal substrate with a non-aqueous treating composition consisting essentially of a novolac phenol-formaldehyde resin having a molecular weight of from about 300 to about 5,000, and a non-aqueous solvent therefore, for a period of time sufficient to deposit less than about 400 milligrams of said novolac resin per square foot of said metal substrate and thereafter heating the treated metal substrate at a temperature of from about 190 to about 270 C. for a period of from about to about 180 seconds in the presence of an oxygen-containing atmosphere.

2. A process as defined by claim 1 wherein the novolac phenol-formaldehyde resin is an ortho-novolac phenolformaldehyde resin.

3. A process as defined by claim 2 wherein the resin has a molecular Weight of about 1000.

4. A process as defined by claim 1 wherein the novolac phenol-formaldehyde resin is a random novolac phenolformaldehyde resin.

5. A process as defined by claim 4 wherein the resin has a molecular weight of about 1000.

6. A process as defined by claim 1 wherein the resintreated metal substrate is heated at a temperature of from about 190 to about 205 C. for a period of from about 60 to about 180 seconds.

7. A process as defined by claim 1 wherein the solvent of the resin treating composition is acetone.

8. A process as defined by claim 1 wherein the novolac phenol-formaldehyde resin treating composition has a resin content of from about 1 to about 10 percent by weight.

9. A process for the after-treatment of a phosphatized metal substrate which comprises contacting said metal substrate at a temperature of from about to about C. with a non-aqueous treating solution consisting essentially of a novolac phenol-formaldehyde resin having a molecular weight of from about 300 to about 5,000 and a non-aqueous solvent therefore, said solution containing from about 1 to about 7 percent by weight of novolac phenol-formaldehyde resin, for a period of time sufiicient to deposit less than about 400 milligrams of novolac phenol-formaldehyde resin per square foot of said metal substrate, and thereafter heating the treated metal substrate at a temperature of from about 190 to about 270 C. for a period of from about 15 to about 180 seconds in the presence of an oxygen-containing atmosphere.

10. A process for rendering a metal substrate corrosion-resistant and paint-receptive, which process comprises:

(a) phosphatizing said metal substrate with an iron or zinc phosphate phosphatizing solution;

(b) drying the phosphatized metal substrate at a temperature of from about to about C. for a period of from about 120 to about 30 seconds;

(0) contacting the metal substrate with a non-aqueous composition consisting essentially of a novolac phenol-forrnaldehyde resin and a non-aqueous solvent therefor, said novolac phenol-formaldehyde resin having a molecular weight of from about 300 to about 5,000 and present in said composition in an amount of from about 1 to about 10 percent by weight, for a period of time suflieient to deposit from about 4 to about 400 milligrams of novolac phenolformaldehyde resin per square foot of surface area of said metal substrate; and

(d) thereafter heating the treated metal substrate at a temperature of at least about C. for a period of at least about 30 seconds in the presence of an oxygen-containing atmosphere.

11. A process as defined by claim 10 wherein the resin is an ortho-novolac phenol-formaldehyde resin.

12. A process as defined by claim 10 wherein the resin has a molecular weight of from about 300 to about 1000.

13. A process as defined by claim 10 wherein the novolac phenol-formaldehyde resin is a random novolac phenol-formaldehyde resin.

14. A process as defined by claim 13 wherein the resin has a molecular weight of from about 300 to about 1000.

15. A process as defined by claim 10 wherein the resintreated metal substrate is heated at a temperature of from about 190 to about 205 C.

16. A process as defined by claim 10 wherein the sol vent of the resin treating composition is acetone.

17. A process as defined by claim 10 wherein the novolac phenol-formaldehyde resin treating composition has a resin content of from about 3 to about 7 percent by Weight.

18. A process for rendering a metal substrate corrosion-resistant and paint-receptive, which comprises:

(a) phosphatizing said metal substrate with an aqueous iron or zinc phosphatizing solution;

(b) removing excess Water to provide a damp phosphate coating on said metal substrate;

(c) contacting the phosphatized metal substrate with a non-aqueous composition consisting essentially of a novolac phenol-formaldehyde resin and a non-aqueous solvent therefor, said novolac phenol-formaldehyde resin having a molecular Weight of from about 300 to about 5,000 and present in said composition in an amount of from about 1 to 10 percent by weight, for a period of time suificient to deposit from about 4 to about 400 milligrams of novolac phenol-formaldehyde resin per square foot of surface area of said metal substrate; and (d) thereafter heating the treated metal substrate at a temperature of at least about 190 C. for a period of at least about 30 seconds in the presence of an oxygen-containing atmosphere. 19. A process as defined by claim 18 wherein the resin is an ortho-novolac phenol-formaldehyde resin.

20. A process as defined by claim 19 wherein the resin has a molecular weight of from about 300 to about 1000. 21. A process as defined by claim 18 wherein the resin is a random novolac phenol-formaldehyde.

22. A process as defined by claim 21 wherein the resin has a molecular weight of from about 300 to about 1000.

23. A process as defined by claim 18 wherein the solvent of the resin treating composition is acetone.

24. A phosphatized metal substrate treated by the process which comprises contacting said metal substrate with References Cited UNITED STATES PATENTS 2,703,768 3/1955 Hall 1486.l5 R 3,471,443 10/ 1969 Bernstein 26017.2 X 2,321,627 6/1943 Rothrock 260l4 X 3,227,686 1/1966 Fitko et al 117-132 BF X 3,156,670 11/1964 Soldatos 1l7--132 BF X ALFRED L. LEAVITT, Primary Examiner C. WESTON, Assistant Examiner US. Cl. X.R.

117132 BF; l486.15 Z

TJNTTTD STATES PATENT oTTTtT QER'llZFlCAlE 6T QGRREQTWN Patent No. 749,611 Dated July 31 1973 Inv n Edward Leon and Malcolm H Shatz It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 63: "discolor to bleed" should read---discolor or to bleed.---

Column 2 line 15: '"chrominum phosphatized" should read ---chromium rinsed phosphatized---.

Column 1-, line 59: "process or the present" should read---process of the present---.

Column 5 line 71: ",or to subsequently applied should read---or to thesubsequently aPPli d--= line 33: "test, arhesion was" should read --te'st, adhesion was- -g line 39: "panel is cleaned" should read ---panel is cleansed---;

line 59: "100 percent huimidity for" should read--l00 percent humidity for---.

Column 9, line 56: "an undercuting of less" should read---an undercutting of less---.

Signed and sealed this 19th day of February 1-974.

(SEAL) Attest: i W m i r EDWARD M, FLETCHER,JR. C ALL DANN Attesting Officer Commissioner f Patents FORM (0459) I uscoMM-oc 60376 P69 US. GOVERNMENT PRINTING OFFICE: 969 0-355-33 

